Patches for dermal and transdermal drug delivery with medically active ingredients as well as wound dressings with active ingredients incorporated are well-known in the art. The active ingredients may be incorporated in a dressing by different means, e.g. being dispersed or soluted in an adhesive or absorbent layer or they may be coated on the skin facing surface of the dressing or patch. When the active ingredient is to be delivered topically, e.g. in the treatment of wounds, corns or warts, the active ingredient may be located as one or more separate zones in the adhesive surface of the dressing.
Problems may arise when the zones comprising active ingredients are placed in direct contact with the other components of the dressing such as the surrounding adhesive or absorbent component. The other components of the dressing may migrate into the zone comprising the active ingredients, damaging or altering the properties of the active ingredients, as well as migration of the active ingredients into the surrounding components is also highly undesired as the active ingredient will spread beyond the target area. In some cases the active ingredients may be aggressive to the surroundings, e.g. in the case of acids, and may attack and damage the other parts of the dressing.
A way of decreasing these problems is to introduce a barrier layer separating the active ingredient from the adhesive. The barrier layer may be in the form of a polymer or metal layer impermeable to the active ingredient and to the surrounding dressing materials such as the adhesive.
In U.S. Pat. No. 4,711,781 is disclosed a drug delivery device comprising a plurality of separate medicated zones on a carrier, the medicated composition being separated from the carrier layer by a barrier layer. The barrier layer is in the form of flat circular pieces under the medication dots. Cup-shaped barriers are also known in the art.
However, even when using these barrier layers/cups, migration is still a problem. It is difficult, seen from a production point of view, to handle the border line between the barrier layer and the surroundings. The adhesive as well as the medication tends to migrate anyway. Furthermore, many medical adhesives tend to cold-flow during storage or use.
GB Patent Application No. 2 184 016 discloses a transdermal device for administration of medicaments. The device has a cup-shaped barrier layer enclosing the active agent, the rim of the cup extending into a flange. The problem of migration during storage is solved by sealing the flange to the release liner. However, the sealing process adds another step to the production process as well as the strength of the seal may be difficult to control, causing a risk that the active agent may follow the release liner instead of the device when separated before use.
Thus there is still a need for a medicated patch where the migration of the medication is minimized.
It has surprisingly been shown that by providing the barrier layer separating a first and a second layer with a flange on which flange the second component only is present in a thin coating the migration is reduced to an acceptable level.